Two diffusion layers are provided in an element area. A tunnel insulating film is provided on the surface of the element area between the two diffusion layers. A charge storage layer is provided on the tunnel insulating film. A first insulator provided on the upper surface of the charge storage layer. An inter-electrode insulating film provided on the first insulator, on the side surface of the charge storage layer in a first direction and on the isolation insulating film. And a control gate electrode extends in the first direction and covers the charge storage layer via the first insulator and the inter-electrode insulating film. The first insulator is thicker than the inter-electrode insulating film, and the inter-electrode insulating film has a first slit on the first insulator.